In this series of seven blogs, we will cover the information you need to know about charging battery powered electric vehicles (EVs). To make the topic easier to digest, we have broken it into seven short blogs, namely:
- Part 1 – Battery and battery charging basics
- Part 2 – Battery performance measures
- Part 3 – EV battery charging – charging levels and home charging
- Part 4 – EV battery charging – outside the home; connectors and charging companies
- Part 5 – EV battery charging – problems with public charging stations; EV charging costs versus ICE-powered fueling costs
- Part 6 – Looking at EV charging’s big picture
- Part 7 – Trends in solar power that will accelerate the move to electric vehicles
Electric Vehicle Battery Charging:
In part because there are few established standards in this rapidly growing electric vehicle field, charging the full range of electric vehicles globally available today is more complex than it should be. In this section we will examine the physical charging hookup for electric vehicles, namely cables and plug/connector configurations.
Charging Levels:
There are currently three “levels” of electric vehicle battery charging available, with a fourth on the horizon. These levels describe the rate of charging, which, of course, plays a significant role in determining how long it takes to charge up any one vehicle’s battery.
Level 1 Chargers:
Level 1 chargers basically include charging from normal (in the US) 120 volt Alternating Current (AC) household electricity – your normal wall outlet. They deliver a charging power of about 1 to 1.9 kW, with a peak current of about 16 amps. This charging rate adds about 3 to 6 miles of range per hour of charging. The outlet used for this should be on a dedicated circuit, with a 20 amp circuit breaker, and thus requires 12 gauge wiring – not the 14 gauge wiring found in a lot of modern homes’ 120 volt outlet circuits.
Level 2 Chargers:
Level 2 charging is done from a 240 volt single phase AC outlet that can deliver some 3 to 20 kW of power. Initially, Level 2 started in 2001 at about 7.68 KW of power which meant a maximum of about 32 amps of current. The latest Level 2 chargers deliver about 19.2 kW of power with a maximum of about 80 amps of current. The typical home charger’s 32 to 40 amp Level 2 charging rate adds about 15 to 25 miles of range per an hour of charging to a typical EV battery. An 80 amp commercial Level 2 charger adds about 65 miles of range per charging hour.
Level 3 DC Fast Charge (DCFC) Chargers:
Level 3 chargers charge from Direct Current (DC), not AC. As such, this charging bypasses the vehicle’s battery management system (BMS) and goes straight into the vehicle’s battery bus bar. Level 3 chargers deliver some 20 to 350 kW of power, thus enabling significantly faster charging times than Levels 1 and 2. Typically Level 3 chargers deliver an 80% battery charge typically good for about 120 miles in 20 to 30 minutes.
Tesla’s V3 Superchargers deliver 250 kW of power.
Tesla has teased a new 4th level of charging – – their “Megacharger”. Undoubtedly, this will be (need to be) used for charging their Semi trucks that are likely to have multiple battery packs. Indeed, these trucks are likely to be charged by anywhere from two to four charging cables simultaneously in order to charge the trucks’ several batteries in less than 30 minutes.
It should be noted that independent of the charger used, electric vehicles have limits to the charging power that can be applied to recharge their batteries. These limits are established to prevent overheating and resulting battery damage. As an example, Tesla’s Models S and X have a maximum charge power of 120 kW. At that rate they can attain an 80% charge in some 30 to 40 minutes. On Tesla’s Models 3 and Y, the maximum charge power is 250 kW, resulting in an even faster charging time.
The current highest charging power in use is for Porsche’s Taycan at 270 kW, with plans to offer 350 kW in the near future. Audi’s e-tron charges at 150 kW by comparison.
Wireless charging:
New inductive or “wireless” charging technology is becoming more popular. It is used in Europe to recharge city busses, with a charging pad at most bus stops so the bus’s battery is recharged a bit at every stop. These charging units consist of a charging pad attached to the floor or street, a receiving unit attached to the bottom of each vehicle, and a terminal that can include payment capabilities to recognize one or more vehicles. Currently, for automotive electric vehicles, these wireless charging units are limited to Level 2 charging – 240 volts AC, and about 3.3 to 20.0 kW of power.
Home charging:
Level 1: Home charging is straightforward. For Level 1 charging that is sufficient for many people, all you need is the aforementioned properly rated 120 volt AC standard wall outlet (NEMA 5-20) on its own dedicated circuit with a 20 amp circuit breaker. After all, most people only drive about 35 miles a day on average. Furthermore, their electric vehicle, if used in a day, sits unused in the garage roughly 12 hours overnight. So just plug it in and top the vehicle’s battery up every night or every other night, just as you do with your cellphone. Start every driving day with a “full tank”….errrr, a fully charged vehicle battery.
Level 2: For those people who drive longer distances, or who want to charge less frequently, installing a Level 2 charger in their garage is relatively easy and inexpensive – the equivalent of adding a 240 volt AC outlet for a clothes dryer. This does require the expertise of a licensed electrician to analyze whether your existing home circuit breaker/distribution panel has the capacity for another 240 volt AC circuit breaker and to make the charger outlet connection to your home’s wiring/circuit breaker panel. Depending on where you live in the US, these tasks alone from an electrician might run you two to three hundred dollars. Buying the parts – a 240 volt AC circuit breaker, the wall box, the plug receptacle (NEMA 14-50), and the electrical wire is also relatively inexpensive, especially if you buy the parts yourself to avoid an electrician’s markup. You can get these items at any Lowes or Home Depot.
Often the larger part of a 240 volt AC outlet installation in a garage is installing the outlet box in the wall and running the wiring behind your walls’ sheetrock from the outlet location to the circuit breaker panel. This is basically carpentry and painting work that electricians don’t like to perform. If you run the wiring inside the wall, you will have to do some sheetrock and patching work, as well as repainting to make things look the way the garage originally looked. Of course, if you don’t care about looks, you could run the wiring and place the outlet box outside the wallboard, being sure to attach the outlet box to not solely the sheetrock or plasterboard, but securely to a wall stud or to a board attached to two wall studs.
Depending on the length of your outlet’s wiring run from the circuit breaker box, you may require either 8 or 10 gauge wiring. The longer the wire run, the lower the wire gauge number. Your electrician can advise you on this.
You can also buy charging cable kits from various suppliers. These include the box to install on your garage wall, as well as the cable from the wall outlet to your particular electric vehicle.
The next blog in this series is: EV battery charging – outside the home; connectors and charging companies
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